1. Field of the Invention
The invention relates to the field of electronically scanned radar antennas and in particular to a continuous ferrite aperture subarray for an electronically scanned antenna intended to operate at about 94 GHz or higher.
2. Description of the Prior Art
Various means for effecting electronic scanning of an antenna aperture are known. Such scanning of phased arrays has been described in the literature including the phased array described in Radant: New Method of Electronic Scanning, by D. Herrick, C. Chekroun, Y. Michel, R. Pauchard and P. Vidal appearing in Microwave Journal, Vol. 24, No. 2, February 1981 at page 45. A copy of that article accompanies this application for patent.
Several patents discuss the steering of a beam of electromagnetic energy by passing the energy through a ferrite block in which a controllable non-uniform magnetization pattern has been established. The patent to R. E. Johnson, U.S. Pat. No. 3,369,242 is illustrative of the technique and provides a good background for the present invention. A copy of that patent accompanies this application for patent, and the teachings of that patent are incorporated in full herein by this reference for background purposes.
A second patent to Johnson, U.S. Pat. No. 3,534,374 combines resonant cavities with the teaching of the earlier Johnson patent to achieve what is claimed to be a highly efficient scanning antenna. The electromagnetic energy is reflected back and forth across the resonant cavity, each reflection increasing the amount of phase shift (and hence increasing the scan angle) of the output beam. A copy of that patent also accompanies this application for patent.
An antenna array system using diode phase shifters is shown in U.S. Pat. No. 3,305,867 issued Feb. 21, 1967 to A. R. Miccioli et al, and a copy of that patent accompanies this application for patent.
The conventional phased array antenna comprises a number of discrete radiating elements. The size of each element is dependent upon the intended operating frequency of the antenna array. Typically each discrete element has a height and width equal to one-half wavelength (.lambda./2). Thus, for an antenna operating at 94 GHz and constucted according to conventional design procedure, each radiating element in the array would measure 1.6 mm.times.1.6 mm. The fabrication tolerances and the complexity of the corporate feed for such an array structure make the discrete element phased array approach not practical for antennas operating at frequencies in the 94 GHz range and higher.